Greases thickened with keto fatty acid lithium soaps or keto cyanoethylated fatty acid lithium soaps

ABSTRACT

KETO FATTY ACIDS OR DERIVATIVES OF KETO FATTY ACIDS ARE CYANOETHYLATED AND THE RESULTING THREE CARBON CYANOETHYL BRANCHED CHAIN FATTY ACIDS ARE MIXED WITH AN APPROPRIATE AMOUNT OF A DIESTER OR A PETROLEUM BASE OIL. THE MIXTURE IS THEN REACTED IN SITU WITH A DILUTE AQUEOUS SOLUTION OF LITHIUM HYDROXIDE TO BOTAIN A STABLE GREASE

United States Patent US. Cl. 252-33.6 Claims ABSTRACT OF THE DISCLOSUREKeto fatty acids or derivatives of keto fatty acids are cyanoethylatedand the resulting three carbon cyanoethyl branched chain fatty acids aremixed with an appropriate amount of a diester or a petroleum base oil.The mixture is then reacted in situ with a dilute aqueous solution oflithium hydroxide to obtain a stable grease.

This is a division of application Ser. No. 275,010, filed July 25, 1972.

A non-exclusive, irrevocable, royalty-free license in the inventionherein described, throughout the world for all purposes of the UnitedStates Government, with the power to grant sublicenses for suchpurposes, is hereby granted to the Government of the United States ofAmerica.

This invention relates to lithium polycyanoethylated keto fatty soapsand more specifically to the use of such soaps to make multipurposegreases.

Small amounts of certain chemical compounds are commonly added tolubricants to improve their physical properties. Typical additivesinclude oxidation or corrosion inhibitors, wear improvers, waterrepellents, and dyes. One problem in formulated greases containingadditives is that in Storage and in use these additives tend to migratein the base oil and in extreme cases cause the grease to separate.Another problem is the frequent tendency for two additives to beincompatible which complicates the task of formulation.

Most lubricants are blended with an additive to improve their anti-wearfunction. The soaps of this invention improve the wear properties of thebase oils with which they are mixed without use of additives. Anotherimportant feature of this invention is that the functional groupsresponsible for anti-Wear and grease forming properties are incorporatedinto the same molecule. Consequently, it is impossible for migration orincompatibility to occur in greases made from these soaps.

The polyfunctional fatty soaps of this invention form two classes ofstable greases, one based on diester type oils, the other on petroleumoils. The diester based greases have good anti-wear properties andbetter than average thermal stability while the petroleum based greaseshave good thermal stability and better than average anti-wearproperties.

An object of this invention is to prepare stable greases by dispersingpolyfunctional soaps in synthetic base oils of the diester type.

Another object of this invention is to prepare stable greases bydispersing polyfunctional soaps in petroleum oil of lubricatingviscosity such as 100 paraflin oil.

Still another object is to provide polyfunctional fatty soap derivativesthat impart thermal stability and antiwear properties to greases.

In general, according to this invention the above objects areaccomplished by dispersing in petroleum oil or in a 3,836,468 PatentedSept. 17, 1974 synthetic oil of the diester type, a polyfunctional fattysoap of the general formula.

wherein the sum of x and y is a number from 5 to 17 and R, R R and R arehydrogen or (CH2)2CEN.

As seen in the formula above, these fatty derivatives are novelcompounds in which from 1 to 4 three carbon side chains having aterminal nitrile groups are attached to the carbons and to the ketone.

Suitable starting materials for the greases formed in this invention areketo fatty acids or their derivatives either naturally occuring orsynthesized by suitable known procedures. The keto fatty derivative isdissolved in an excess of acrylonitrile containing a small amount ofwater to inhibit polymerization. Addition of a catalytic amount ofstrong base to this mixture causes the formation of products in whichfrom one to four fl-cyanoethyl groups are attached to the carbon atomswhich are adjacent to the ketone group. The product mixture is recoveredafter acidification of the reaction mass.

The unrecated fatty ketone is recovered by extracting the reactionmixture with hexane. The [3-cyanoethyl branched fatty acids are thenmixed with the appropriate amount of the desired base oil. The mixtureis then treated in situwith a dilute aqueous solution of lithiumhydroxide. It was found desirable to add about 2% of an emulsifier,sorbitan monooleate. The mixture is stirred to 110 C. until the properdegree of dehydration is obtained to yield a stable grease with thedesired consistency. The degree of cyanoethylation of the keto fattyacid will vary depending on conditions such as temperature andconcentration of reactants. For the purposes of this invention,conditions were chosen to give an average of two cyanoethyl groups permolecule.

The diester based greases formed from this lithium polycyanoethylatedfatty soap show considerably better anti-wear properties and somewhatbetter thermal stability than a diester based grease prepared fromsodium stearate. The petroleum based greases formed from this fatty soapderivative have improved anti-wear properties and much better thermalstability than a standard sodium stearate petroleum based grease.

In the preparation of the cyanoethyl fatty grease precursor, suitableketo fatty acids may vary in chain length from 10-22 carbon atoms withthe carbonyl group attached at any point on the chain.

The diester based greases can be formulated using any of the commoncommercial diester oils such as di(2-ethyl hexyl) sebacate (D.O.S.).Suitable oils for the petroleum based greases may be any hydrocarbon oilof lubricating viscosity such as parafiin oil.

The amount of polycyanoethyl fatty soap used in this invention to formgreases is generally less than 20% by weight of formulated grease.

It is important that the grease formed is not overheated or the smallamount of water necessary for the oil, water, soap complex will bedriven oif causing the soap to precipitate.

The ureacted keto fatty acid can be recovered or may be left in thereaction mixture. Its presence does not affect the grease formingproperties but does reduce the beneficial effects on wear and thermalproperties.

The thermal stability properties of the greases described in this patentwere determined using the dropping point method (AST M D 566). Thisprocedure measures the temperature at which the grease passes from asemisolid to a liquid state and is a qualitative indication of the heatresistance of the grease.

Anti-wear properties were determined using the Shell Four Ball WearTester as described by ASTM designation D226664T. Federal test methodstandard No. 7916. Approximately 10 ml. of the grease to be tested isplaced in the test cup so that the three bottom stationary balls arecovered. After positioning the cup on its stand in contact with thefourth ball, the grease was heated to 75 C., a 40 kg. load was placed onthe weight tray, and the upper ball was allowed to rotate at 1200 rpm.for 1 hour. The diameters of the scars worn on the three stationaryballs were measured by means of a low power microscope. The hardness ofthe greases was determined with a Penetrometer as described by ASTMdesignation D217-48. A microcone was used to check the consistency ofsmall samples.

The invention is illustrated by the following examples.

EXAMPLE 1 50 g. (0.186 moles) of methyl 12-ketostearate was dissolved in336 g. (6.3 moles) of acrylonitrile containing 8 ml. water. To thismixture was added with stirring, 24 ml. of a 40% aqueous solution ofbenzyltrimethylammonium hydroxide. The mixture was allowed to stir for 1hour and then diluted with 300 ml. of water and 200 ml. of acetone. Themixture was then acidified with HCl and extracted with three 400 ml.portions of ether. The combined extracts were washed with water, driedover sodium sulfate and evaporated to a residue weight of 68.4 g.Gas-liquid chromatography (GLC), thin layer chromatography (TLC), andinfrared (IR) analysis confirmed that the residue was predominately amixture of mono, di, tri and tetra cyanoethylated ketostearate isomersplus some unreacted ketostearate. Recrystallization from hexane removedthe unreacted ketostearate. GLC and elemental analysis showed therecrystallized product averaged about two cyanoethyl groups permolecule.

Preparation of Diester Grease To a vigorously stirred mixture of 8.5 g.di(Z-ethylheXyUsebacate (D.O.S.), 1.5 g. cyanoethylated 12-ketostearicacid, 0.2 g. sorbitan monooleate and 1 ml. water at 110 C. was added adilute solution of lithium hydroxide until the acid was neutralized.Stirring and heating at 110 C. was continued until the mixture began tothicken. It was then allowed to cool to room temperature with stirring.A stable grease of grade 1 hardness formed having an average wear scarof 0.564 mm. and a dropping point of 379 F.

Preparation of Petroleum Grease Using the above procedure butsubstituting 8.5 g. of 100 paraffin oil for the base oil, thecyanoethylated 12- ketostearic acid gave a stable grease of grade 1hardness having an average wear scar of 0.715 mm. and a dropping pointof 383 F.

EXAMPLE 2 5.3 g. (0.018 moles) of 9(10) ketostearic acid was treatedwith benzyltrimethylammonium hydroxide in a 40% methanol solution untila pH of 10 was reached. The methanol was driven off with heat, and thesoap product was dissolved in ml. pyridine, 1 ml. water and 50 ml.acrylonitrile (0.75 moles). To this mixture was added slowly withstirring 2.5 ml. of a 38.5% aqueous solution of benzyltrimethylammoniurnhydroxide. After a half hour of stirring the reaction was diluted with20 ml. H 0 and 10 ml. acetone and then HCl was added until a pH of 2 wasreached. The resulting mixture was extracted with three 50 ml. portionsof ether. The combined extracts were washed with water, dried oversodium sulfate and evaporated to a residue weight of 6.4 g. GLC analysisconfirmed that the residue was predominantly a mixture of mono, di, triand tetra cyanoethylated ketostearate isomers plus some unreactedketostearic acid. Recrystallization from a benzene ether mixture removedthe unreacted material.

Preparation of Diester Grease In a manner similar to that of Example 1,a diester grease was prepared from the cyanoethylated 9(10) ketostearicacid. This product formed a stable grease of grade 0 hardness having anaverage wear scar of 0.524 mm. and a dropping point of 339 F.

Preparation of Petroleum Grease A paraffin oil grease was prepared as inExample 1. This 100 parafi m oil based grease formed from thecyanoethylated 9(10) ketostearic acid gave a stable grease of grade 1hardness having an average wear scar of 0.677 mm. and a dropping pointof 358 F.

Attempts were made to substitute sodium, calcium, and aluminum in placeof lithium but only negative results were obtained. Greases could not bemade with these substitutes.

We claim:

1. A multipurpose grease comprising a major amount of lubricating oilselected from the group consisting of paraffin oil and aliphatic diesteroil and a minor thickening amount of a lithium soap of the generalformula R o R i II I 6 0113((3112)x-CC--C(CH2) COOL1 wherein the sum ofx and y is a number from 5 to 17 and R, R R and R are selected from thegroup consisting of hydrogen and (CH2)2CEN.

2. The grease of Claim 1 wherein the lubricating oil is paraflin oil.

3. The grease of Claim 2 wherein the sum of x and y is 13.

4. The grease of Claim 1 wherein the lubricating oil is di(Z-ethylhexyl)sebacate.

5. The grease of Claim 4 wherein the sum of x and y is 13.

References Cited UNITED STATES PATENTS 3,009,878 1l/l96l Eckert 252413,278,431 10/1966 Morway et al 25239 DANIEL E. WYMAN, Primary ExaminerI. VAUGHN, Assistant Examiner US. Cl. X.R. 2524l, 400

